In consideration of the fact that there is an ongoing increase in (bio-)chemical and genetic analyses and assays, a strong demand for the automated pipetting of fluids can be observed. For this reason, in recent years, many efforts have been made to develop new automated pipetting apparatus, e.g., enabling plural pipetting operations in parallel. Automated pipetting apparatus typically use plunger pumps which in order to enable precise pipetting of fluids have to be specifically sized to the intended range of pipetted fluid volumes. It is further known to use liquid system fluid which due to a reduced compressibility and lower temperature-induced variations compared to the otherwise purely gaseous system fluid improves preciseness of pipetting operations.
In order to avoid contamination of fluids, automated pipetting apparatus usually may be brought into a washing mode for performing washing operations, e.g., in-between consecutive pipetting operations. Due to the normally much greater fluid volumes required for washing operations compared to the pipetted fluid volumes, it is not appropriate to use plunger pumps for both pipetting and washing operations. In order to avoid such drawback, pumps other than plunger pumps which can be used for both pipetting and washing operations such as pumps of the rotary displacement pump type have been envisaged for use in automated pipetting apparatus.